External Solar Shading Research Articles

Is there an optimum balance between indoor environment, energy consumption and health?

This study investigates the pros and cons of passive strategies in the indoor environment (IE) in relation to energy consumption (EC). It is widely accepted that IE improvements often require energy, particularly for thermal and atmospheric IE. As a result, demands for energy savings might compromise the indoor environmental comfort and health. However, the energy consumption can be reduced by introducing passive measures both regarding temperature and ventilation rates. To investigate this, measurements of temperature and ventilation rates were carried out in eight newly built single-family homes and four renovated single-family homes in a Danish context for three years. The study analyzes the effect of passive cooling using different types of solar shading. The findings show that external solar shading can effectively reduce high temperatures without additional energy consumption for cooling in a Scandinavian context. Also, the difference between mechanical and natural ventilation on CO2 levels in bedrooms and children’s rooms in relation to sleep quality are analysed. Here the results show, that natural ventilation is insufficient to ensure healthy sleeping conditions when it comes to proper ventilation rates and air quality. Supplemental ventilation by either window airing or mechanical aid is necessary.

Detailed assessment of hybrid ventilation control system in a mixed-mode building in cold climate

This paper investigates a hybrid ventilation control method for a mixed-mode office landscape in a cold climate, i.e. Norway. The mixed-mode building utilizes a hybrid ventilation system that combines natural ventilation through automatic window opening with a balanced mechanical ventilation system controlled by demand control ventilation (DCV) method. For natural ventilation, the windows consist of two parts: the upper part which is openable and the lower part that is not openable and equipped with external solar shading. From a control point of view, the article elaborates a control algorithm for the proposed hybrid ventilation based on various parameters including outdoor air temperature, indoor air temperature, CO2 level, maximum air change per hour (ACH), operation schedules, and heating/cooling setpoints. The simulation results obtained from the hybrid ventilation and mechanical ventilation cases are compared based on thermal comfort, CO2 level, and energy savings. The primary results show that the proposed hybrid ventilation control method can satisfy the thermal comfort and CO2 level requirements while reducing the energy use for fan and ventilation cooling by approximately 55% and 45%, respectively. While the impact on energy consumption for space and ventilation heating is negligible.

An Appraisal of Double Skin Facade in Building Design: Architectural Intervention and Sustainability

One of the key issues in twentieth-century architecture is the energy problem and daily rise in environmental pollution brought on by the creation of greenhouse gases, particularly in the construction industry. The purpose of the research that follows is to investigate how well buildings heat up while also updating double-skinned facades to ensure thermal comfort for the residents while using the least amount of energy possible. The thoughtful design of a building's exterior is one of the most crucial ways to conserve energy in that structure. The finest choice for controlling the interplay between the interior and exterior spaces is a ‘double-skin facade’. Double-skin facades have been used more frequently recently to increase transparency in both building renovations and new construction. Although glare issues may worsen, double-skin facades improve lighting levels and the outside view. When comparing a typical glass facade to one with an additional layer of glazing, it is possible to reduce heat loss and outside noise. A very critical concern appears to be the protection of external solar shading devices against wind and deterioration. This paper reviews and discusses the earlier research on double-skin building facade systems. The evaluation of a double-skin facade system for long-term building envelope or infrastructure development is the main theme of the paper.

Domestic overheating risks and mitigation strategies: The state-of-the-art and directions for future research

Anthropogenic climate change will likely put dwellings at risk of overheating and potentially increase cooling demand in the decades ahead, leading to higher greenhouse gas (GHG) emissions due to the energy consumed for mechanical cooling. Contemporary constructions with highly insulated fabric have been found to suffer from periodic overheating in today’s climate, the occurrence of which is projected to increase in frequency as the temperature rises. This critical review investigates the factors affecting overheating risks in dwellings and passive cooling strategies to mitigate overheating impacts on occupant thermal comfort and wellbeing. The cooling efficiency of passive strategies is affected by the design, construction and operation of buildings, as well as climate and occupancy. A framework has been developed to illustrate the effect of overheating factors on the cooling efficacy of passive strategies. Findings suggest that a combination of passive strategies is required to minimise overheating risks by the 2080s. External solar shading is the most effective method for retrofitting insulated dwellings. On the other hand, cool paint is ideal for uninsulated dwellings. In addition, thermal mass and natural ventilation require occupant interaction for optimal air circulation and cooling performance.

Green Building Concepts and Technologies in Ethiopia: The Case of Wegagen Bank Headquarters Building

The building sector is a key contributor to climate change, accounting for 40% of global energy consumption and 39% of CO2 emissions. Presently, green buildings have been viewed as crucial strategies to reduce the negative effects of the construction sector. Yet green building research is often carried out in developed countries, while relatively little is known in sub-Saharan African countries. Therefore, this study attempts to investigate the extent of adoption of green building concepts and technologies in Ethiopian buildings, with particular reference to the Wegagen Bank Headquarters building. The study employed an interview, which was underpinned by observation. The quantitative data were analyzed through descriptive statistics while the qualitative data were analyzed through content and context analysis. Results revealed that while the building provides convenient access to transportation; it lacks designated open spaces. Based on the findings, the widely used technologies were energy-saving lighting, highly efficient plumbing fixtures, and external solar shading system. Lack of awareness, lack of policy, insufficient professional skills, the perception that green buildings are expensive, and lack of green building materials hindered the adoption of the concepts. Therefore, the study suggests developing green building policy and rating systems, professional capacity building, and awareness creation as important measures.

Comparative field tests of an electrochromic shading device - thermal and visual comfort

Electrochromic devices (EC), or Smart Windows, are amongst the most promising technologies to increase users’ wellbeing in buildings. A comparative test of EC windows performance was realised in the ZEB Test Cell Laboratory in Trondheim, Norway. Two identical rooms were used for the comparative tests. One of the rooms was equipped with EC devices. The other room was equipped with a traditional insulated glazing unit (IGU) with external solar shading device. Three automatic control strategies were tested in this experiment. The EC device demonstrated a good impact on the thermal and visual comfort when compared to a traditional IGU without moveable shading and a traditional IGU with an external screen.

Multi-Objective Analysis of a Fixed Solar Shading System in Different Climatic Areas

This study tackles the analysis of fixed external solar shading systems. The geometry of a building and of the shading system has been parametrically defined and a genetic optimization analysis has been carried out to identify an architectural solution that would allow the increase of energy savings, through a suitable window-to-wall ratio and an accurate design of the shading device. A multi-objective analysis has been performed with the aim of minimizing the energy consumption for space heating, cooling and artificial lighting, while ensuring the visual comfort of the occupants. The main goal of the study is to explore the influence of climatic context on the optimal design of shading devices. The analysis has been performed for three different latitudes across Europe. In all analyzed cases, a reduction of the annual energy consumption could be achieved, up to 42% if the optimal shading configuration is used. Moreover, the possibility of integrating the shading system with photovoltaic (PV) panels has been considered and the electricity production has been estimated.

Nonuniform Woven Solar Shading Screens: Shading, Mechanical, and Daylighting Performance

This study investigated the potential of using a nonuniform woven panel with nonuniform strips—thick sticks and thin battens—as an external solar shading screen that addressed daylighting, shading, and mechanical performance factors. The sustainable material, namely, bamboo, was used as the demonstration material for the screen. An on-site experiment and ANSYS simulation were carried out to investigate the basic solar optical performance and structural strength of the proposed screen, respectively. Then, a series of daylighting simulations were conducted to optimize the configuration of the screen. The results showed that the nonuniform woven solar shading screen reduced up to 80.3% of the solar radiation gain in a room during summer months while ensuring a relatively even distribution of useful daylight during the year. Moreover, the screen effectively reduced the negative impact of glare to a level below “imperceptible” and enabled a relatively clear view through the window and shading. Regarding the structural strength, the screen with a size smaller than or equal to 1 × 1 m withstood a wind load of 12 m/s. Furthermore, this study proposed two optimal configurations: a screen woven of square sticks and battens with a distance of 10 mm between them, and a screen woven of round sticks and battens with a distance of 8 mm between them. This study illustrated the superiority of the nonuniform woven solar shading screens, which supports a wider application of solar shading screens made of other materials with similar structures and reflectance values.

A pixel counting technique for sun patch assessment within building enclosures

Pixel counting (PxC) emerged as a powerful technique for external solar shading calculations of buildings, providing accurate results with great computational efficiency even for dense geometries. Motivated by this fact and because the technique can be also adapted to cope with interior surfaces without further ado, this paper aims at experimentally evaluating the PxC technique implemented in Domus software for calculating sun patch distribution within building enclosures. For the validation purpose, digital images were taken from the surfaces of an experimental house to compare with the simulation results obtained by using EnergyPlus and two PxC based tools: Domus and Shading II SketchUp plug-in. This first task has shown that the PxC presents results in good agreement with the experimental data, in terms of both location and area of the sun patch. Also, a second case study was constructed to evaluate the capability of PxC for simulating non-convex zones with perforated shading elements. The results, in general, have shown that the PxC can provide accurate results in situations where polygon clipping based algorithms cannot be applied.

A London residential retrofit case study: Evaluating passive mitigation methods of reducing risk to overheating through the use of solar shading combined with night-time ventilation

Overheating in the indoor environment, specifically in domestic homes, schools and healthcare settings has become of great concern to us in the UK. This is due to frequent hot weather events as a result of the continually rising global average temperatures. Overheating is a result of the heat gains associated with occupancy and solar heat gains trapped in the internal environment. The continuing rise in global average temperatures and improved insulation standards necessary to mitigate heat losses during the winter, in conjunction with poorly planned ventilation strategies, are exacerbating overheating during warmer weather conditions. In the last decade, there has been a considerable improvement in reducing heat gains associated with occupancy (from lighting and equipment), thus making solar heat gains more prominent in contributing to overheating. With the rise in the number of buildings that overheat and the rise in the number of associated deaths these contribute to, it is now crucial that passive measures are utilised appropriately, and for building occupants to be educated in how to safeguard their homes against overheating. This research is centred around a real-world monitoring case study and investigates how the proposed passive measures can mitigate overheating risk. These measures include the use of different internal and external solar shading devices combined with a night-time natural ventilation strategy. This study was conducted in a south-west facing, single aspect retrofit apartment building in London between August and October 2016 and 10-min interval data were collected during the daytime over 20 days. Throughout the monitoring period, a controlled window opening strategy was applied in rooms where differing shading strategies were implemented. In the absence of night-time measurements, the rooms were evaluated according to CIBSE TM52 Overheating Criteria to assess the frequency and the severity of overheating and mitigation methods were statistically compared to analyse the difference in internal operative temperature increase according to the type of passive mitigation scenario implemented. The combination of opening windows at night and the closure of shading devices during the day can provide a significant thermal benefit to occupants. The inter-relationship between glazing, shading, ventilation amongst other variables needs to be collectively evaluated at the building design stage to ensure the appropriate design of an effective façade management strategy. Practical application: This study aims to add to the body of knowledge surrounding overheating by investigating the impact that the combination of shading and night-time ventilation strategies can have on a newly refitted, urban apartment. It demonstrates how the frequency, severity and the absolute maximum temperature can be identified using existing industry criteria and then uses this methodology alongside inferential statistics to compare the effectiveness of differing shading strategies when combined with night purge ventilation.

Multivariable Optimization of Dynamic Translucent Solar Screen on West-Facing Offices

Discomfort glare frequently occurs in the west-facing rooms of office buildings during the afternoon. Using conventional opaque and fixed solar screens can obstruct the direct solar radiation, and reduces the glare. However, they may considerably reduce indoor daylighting levels and block the view outside at the same time. Thus, dynamic translucent panels are proposed in this study as external solar shading screens on the west-facing facades. Most importantly, a systematic method is developed to optimize the positions of the panels, addressing both daylighting, glare and view. The optimization algorithm - Artificial Neural Networks, combined with daylighting performance simulations is used to determine the optimal design parameters of the proposed solar shading screens. An office room in Guangzhou is used as a case study to test and optimize the proposed method. The whole study process consists of three steps: simulation, regression, and optimization. The results show that the neural network regression results are very close to the simulation ones. It means that deep neural networks can achieve a relatable regression performance and reduce the optimization time significantly. The optimal positions of the solar screens effectively reduce the glare level and maintain a relatively high indoor daylighting level and a large view field. Furthermore, this study also discusses the different effects of the weights for evaluation indicators on the final optimization results.

Solar control solutions for reducing overheating risks in retrofitted Danish apartment buildings from the period 1850- 1900 – A simulation-based study

Advancing energy efficient renovation solutions in residential buildings necessitate adopting high-insulation and airtightness to avoid heat loss through transmission and infiltration, which can result in overheating. Elevated indoor temperatures have been proved to have a highly negative effect on occupants’ health and well-being. Energy efficient solutions to the problem with overheating include limiting the solar heat gains through the glazed parts of the facade and effective ventilation. A typical Danish residential apartment building from 1850-1900 recently refurbished, was modelled with five different solar shading devices and three typical ventilation solutions. External solar shading could efficiently reduce overheating below the limits specified by the national building regulations in all tested cases. The marquisolette reduced the number of occupied hours with temperature above 27 °C by min. 85%, the external venetian blinds by min. 81%, and the drop arm awning by min. 74% compared to the situation without solar shading. The internal solar shading as venetian blinds and roller blind could reduce the overheating hours by 20-40%, which was efficient only in combination with mechanical ventilation in case of south and east building orientations.

Effect of external solar shading usage on energy consumption and thermal comfort in the student dormitory in Niš

External fixed shadings are largely used to provide solar protection for building glazed surfaces. They are reducing heat gains and sensational visual discomfort caused by excessive daylighting. This paper presents a comparative study on external aluminium fixed shadings used on a student dormitory on different orientations and different slat angles. The purpose is to determine which slat angles are best to use in different orientations, from the point of view of energy consumption, thermal comfort, and daylighting. An analysis of annual energy consumption of the student dormitory was performed by using the software EnergyPlus, whereas the model of the building was created using SketchUp and OpenStudio software. Then, a parametric study was carried out by changing slat angles and building orientations, in order to find the best-balanced results with no occupant discomfort and possible energy savings. Results have shown that by considering the most balanced results between energy savings and thermal comfort, the best angles of the slats are from 105˚ to 120˚ on the south side, and from 45˚ to 75˚ on the east and west sides. By installing external shading devices, indoor thermal conditions are improving and may lead to significant energy savings, compared to a building without shading devices.

Effect of fenestration geometrical factors on building energy consumption and performance evaluation of a new external solar shading device in warm and humid climatic condition

Glazed facades are being increasingly used in modern buildings in order to improve the daylight availability in the interiors, offer better external views and also add to the architectural beauty of the building. However this increased usage of glazed facades is leading to higher solar gain inside the building which is becoming a major issue in hot climatic regions. External shadings are thus used to protect the buildings from direct solar radiation which cause high solar gain as well as discomfort due to glare. The present study summarizes the effect of geometrical factors like window to wall ratio (WWR) and window positioning on the heating, cooling and lighting energy consumption of a South facing building cell in warm and humid climate. The performances of different commonly used external solar shading devices have been compared. The study also proposes the design of an external shading device which, when compared with the existing shading designs, leads to reduction in annual energy consumption of the building. The simulations were carried out using building energy simulation program EnergyPlus for the warm and humid climate of Kolkata, India. In order to validate the applicability of the new shading in other locations experiencing similar climate, the performance of the proposed shading was also evaluated for two other locations- Naples in USA and Hanoi in Vietnam. In both of these cases the new shading offered better performance than the other existing shading designs.

Glazing’s techno-economic performance: A comparison of window features in office buildings in different climates

The use of glass in buildings has a considerable impact both on comfort levels and energy performances, since glazed components protect from external environmental conditions, provides daylighting, view and also ventilation if they are openable. Starting from the second half of the 19th century, the architectural design used to give an increasingly important role to the glass, particularly in non-residential buildings, almost in every kind of climatic conditions. In this context, the present work aims to assess the techno-economic performance of glazing with various thermophysical and optical properties and different glass/wall ratios, coupled with internal/external shading systems, considering the application on an office building in 3 different representative European climates. The obtained results demonstrate that there is a negative impact of solar gains on the yearly energy balance of modern office buildings, where thermally-insulated envelopes enhance overheating even in cold climates. Because of this, the most reasonable solution to decrease the yearly energy consumption is to limit the amount of glazing or to use external solar shading devices. It can be also stated that, under a global-cost perspective, the best cost-effectiveness is achieved using a solar control glazing without any shading. If, however, the cost of discomfort due to glare is accounted, the use of solar shading devices emerges as the most convenient option in all analysed cases.

Theoretical analysis of the performance of different cooling strategies with the concept of cool exergy

The whole chains of exergy flows for different cooling systems were compared. The effects of cooling demand (internal vs. external solar shading), space cooling method (floor cooling vs. air cooling with ventilation system), and the availability of a nearby natural heat sink (intake air for the ventilation system being outdoor air vs. air from the crawl-space, and air-to-water heat pump vs. ground heat exchanger as cooling source) on system exergy performance were investigated.It is crucial to minimize the cooling demand because it is possible to use a wide range of heat sinks (ground, lake, sea-water, etc.) and indoor terminal units, only with a minimized demand. The water-based floor cooling system performed better than the air-based cooling system; when an air-to-water heat pump was used as the cooling source, the required exergy input was 28% smaller for the floor cooling system. The auxiliary exergy input of air-based systems was significantly larger than the water-based systems.The use of available cool exergy in the crawl-space resulted in 54% and 29% smaller exergy input to the power plant for the air-based and water-based cooling systems, respectively. For floor cooling, the exergy input to the power plant can be reduced by 90% and 93%, with the use of ground, and use of the ground and the air in the crawl-space, respectively. A new approach to exergy efficiency was introduced and used to prove that the exergy supply from the ground matches well with the low exergy demand of the floor cooling system.

Analysis of the predicted effect of passive climate adaptation measures on energy demand for cooling and heating in a residential building

Both new and existing buildings need to be adapted to climate change, in order to keep providing a comfortable and healthy indoor climate. Preferably, the adaptation measures applied at the building level scale do not require additional energy (i.e. passive measures). Previous studies showed that passive climate change adaptation measures can have a positive effect on thermal comfort in summer and its shoulder seasons in non-air-conditioned residential buildings. In this paper, the effect of these passive climate adaptation measures – applied at building component level – on the cooling and heating energy demand of a terraced house is analyzed using building energy simulations. It is shown that for this particular case the required cooling energy can be limited to a large extent (59–74%) when external solar shading or additional natural ventilation is applied. In addition, it is shown that for a well-insulated terraced house the energy cost for heating is not strongly affected by the application of passive climate change adaptation measures.

Study of hygrothermal behaviour of a hemp concrete building envelope under summer conditions in France

This paper presents some preliminary investigations about the transient hygrothermal behaviour of a hemp concrete envelope under summer conditions in France. The first part compares the thermophysical properties of hemp concrete to those of other materials used in construction. Then in order to investigate the material hygrothermal behaviour in a building envelope, a coupled heat and mass transfer model is implemented into the simulation environment SPARK and validated with experimental data available from the current literature. Simulations for a room made of hemp concrete are run under summer conditions for three French cities. Our results suggest that in South France the use of hemp concrete in buildings can lead to an indoor superheating for more than 70% of occupation period. These conditions can be improved significantly by using the combined effect of external solar shading, night ventilation technique and high energy storage capacity materials.

Effects of solar shading devices on energy requirements of standalone office buildings for Italian climates

In Europe, the building energy demand is about 40% of the total energy requirement. In order to obtain significant energy saving in this sector, the European Energy Performance Building Directive (EPBD) 2002/91/CE and the EPBD Recast (Directive 2010/31/UE) promote the use of passive strategies for buildings, which improve indoor thermal conditions above all in summer and so allow the reduction of size and energy requirements of air conditioning systems.This paper analyzes the influence of external solar shading devices on the energy requirements of a typical air-conditioned office building for Italian climates. A type of office building widespread in Europe has been considered. The energy saving related to the solar shading refers only to summer air conditioning, but the evaluation has been carried out for the entire year, by using a building energy simulation code. The energy demand of the main technical systems (heating, cooling and lighting) and the energy saving related to the use of solar shading devices have been evaluated, as a function of the most significant parameters, such as the climate, the geometrical characteristics of the shadings and the building, the thermal transmittance of the building envelope and the building orientation. The solar shading devices have shown the highest energy efficiency for warm summer climates: for example, the global annual energy saving related to the use of suitable shading devices has been evaluated between 8% for Milan (the coldest climate) and 20% (for Palermo, the warmest one).

Feasibility assessment of passive cooling for office buildings in a temperate climate through uncertainty analysis

In this paper, the feasibility of passive cooling in newly built office buildings in the temperate climate of Belgium is assessed using the standardized adaptive comfort criteria. This is done through Monte Carlo uncertainty analysis of the simulated weighted exceeding time for different building designs with varying insulation level, glazing-to-wall-ratio, glazing type and air tightness. Two passive cooling schemes are studied: diurnal manual window operation and the combination of diurnal manual window operation and passive night ventilation. Additionally, two possible measures to limit heat gains, external solar shading and daylighting, are considered.The integration of a detailed model of window operation, establishing a real-time coupling between the thermal model and the behavioural model and thus allowing simulating adaptive behaviour, is shown to impact the results significantly and is therefore recommended by the authors.The uncertainty analysis shows that it is possible to cool office buildings solely by diurnal manual window operation, even for highly insulated and air tight buildings. This requires minimizing heat gains to about 900 kJ/m2 per working day during summer months. When a combination of diurnal window operation and night ventilation is available, limiting the heat gains to about 1500 kJ/m2 per working day suffices.